A liquid crystal display device (LCD) has been utilized in various uses of notebook computers, cellular phones, liquid-crystal-display televisions and the like, and it generally consists of a liquid crystal cell comprising a liquid crystal, a polarizing plate, and an adhesive layer or an unreworkable adhesive layer for joining the liquid crystal cell and the polarizing plate.
Also, the polarizing plate used in the LCD generally has a multi-layered structure including a polarizer (sometimes called ‘polarizing film’) obtained by adsorbing and aligning an iodine compound or a dichroic polarizing material on a polyvinyl alcohol (PVA)-based resin film which is elongated in a certain direction; first and second triacetyl cellulose (TAC)-based protective films laminated on both surfaces of the polarizer through an unreworkable adhesive so as to protect the polarizer; and an adhesive layer laminated on one surface of any one of the protective films, which is used for fixing the polarizing plate to a liquid crystal cell.
Recently, the slimness of the LCDs is increasingly demanded in slim wall-mounted TVs, mobile computers, TVs for vehicles, the displays of navigation systems for vehicles, cellular phones and the like. In order to achieve the slimness and light weight of the LCDs, it is necessary to provide an ultra thin polarizing plate (UTP) that allows the whole module of the LCDs to be thinner.
There has been proposed a method for preparing such an UTP by removing one of the protective films from the configuration of the polarizing plate. That is, the UTP has a polarizer being directly laminated with an adhesive layer without a separate protective film. However, such an UTP undergoes the occurrence of severe curl, which may cause bubbles or lifting (peeling) in the bonding interface of the UTP and a liquid crystal cell, thereby deteriorating bonding durability and resulting in appearance defects.
Korean Patent No. 10-1008869 discloses a method for preparing a polarizing plate by laminating transparent protective films having different thickness on both surfaces of a polarizer, which control the moisture ratio of both protective films to inhibit curl. However, this method cannot be applied in an UTP having only one protective film.